Instrumented roller bearing, in particular for control wheel

ABSTRACT

An instrumented roller bearing, in particular for an electrical steering wheel ( 12 ), comprises an outer component ( 1 ) and an inner component ( 6 ) whereof one is mobile in rotation relative to the other which is fixed, through at least a row of rolling elements ( 14 ) arranged between the components, and elements for detecting ( 22, 23, 31 ) the rotating parameters of the rotary component. The bearing further comprises electronic members ( 34 ) for processing signals emitted by the detecting elements and electronic elements ( 35 ) for controlling at least an actuator electrically connected to the device, advantageously arranged on a printed circuit wafer ( 33 ) fixed in rotation.

[0001] This invention concerns an instrumented roller bearing, that canbe used in particular with a control wheel, for example for materialshandling machine or an earth moving machine.

[0002] The roller bearing is of the type comprising an external elementand an internal element, between which there is disposed at least onerow of rollers. One of these elements is fixed with respect to a cage,whereas the other can be driven in rotation by the electrical controlwheel. The instrumented bearing has a means for detecting the rotationparameters of the rotating element, so that it controls an electrical orelectro-hydraulic actuator.

[0003] Increasingly more often, electrical steering control is used inmaterials handling machines, such as fork lift trucks, or certain earthmoving machines. The wheel, whose rotational movement is actuated by thedriver, is mounted on a fixed support by means of one or two rollerbearings, to which a rotation detection system is added, that may or maynot be incorporated into the roller bearings. This detection systemsends a signal that is representative of the rotation of the wheel(angle, direction and angular speed) to a signal processing system, thento an electronic steering logic system which in turn sends appropriatesignals to electrical or electro-hydraulic actuators, that govern thedirection of the wheels of the vehicle according to the orders given bythe driver.

[0004] An example of such a device is illustrated in the French patentapplication 2 782 970, in which a wheel braking system amongst othershas been fitted, in order to generate a resistance torque that makes thevehicle more precise and reliable.

[0005] These devices are already known, and although they aresatisfactory from a technical point of view, they do have certaindisadvantages, in particular as concerns their bulkiness and thecomplexity involved in mounting them onto the vehicle or machine. Infact, the electronic detection system, like the electronic processingsystem and the electronic steering system are generally made in the formof separate units, distant from one another and linked by connectionsystems. Such a scattering of electronic modules has the disadvantage ofmaking them more sensitive to external electromagnetic interference, asthe connector cables act as antennae.

[0006] The reliability of these known systems is also imperfect, giventhat the connector cables are exposed to the risks of being damaged ofbeing torn off or sectioned by accident.

[0007] The purpose of this invention is to eliminate these difficultiesand to create an instrumented roller bearing that is more reliable,easier to mount and more compact than the other devices known untilpresent.

[0008] The instrumented roller bearing of the invention, that can beused in particular for a control wheel of a materials handling machineequipped with an electrical steering control system, has an external andan internal element, one of which rotates while the other is fixed, bymeans of a row of rollers disposed between the said elements. The devicealso has a means of detection of the rotation parameters of the rotatingelement. The device of the invention also includes electronic means forprocessing the signals emitted by the detection means and the electronicsteering means by at least one actuator electrically linked to thedevice.

[0009] In this way, the different electronic modules are groupedtogether inside a particularly compact assembly, which improvesreliability by eliminating all external interference on the connections.The device may be made in the form of a modular assembly that is cheapto manufacture and easy to install.

[0010] The electronic signal processing means allow the final signal tobe processed and adapted to suit the requirements of the application.These means may include in particular a logic BUS type interface totransmission the information detected and to make it reliable, a signalfilter to improve the electromagnetic or electrostatic protection thatis compatible with the environment of the application and a signalredundancy analysis system, with emission of a fault signal in the caseof detection failure.

[0011] The electronic steering means allow the final signal to begenerated in the form of a voltage and/or a current to servo-control oneor more electrical, electronic or electro-hydraulic actuators, actuatingfor example the mechanism for turning the wheels of a vehicle accordingto the angular movement of a control wheel, detected by the detectionmeans.

[0012] In a preferred embodiment, the electronic signal processing meansand the electronic steering means are mounted on a printed circuit boardfixed in terms of rotational movement. Simply changing the printedcircuit board allows the device to be adapted to another application.

[0013] A connector is directly connected to the electronic steeringmeans, and can co-operate with a connector cable linked to the actuatorto communicate the steering orders to the latter.

[0014] A cover preferably encloses the device on the printed circuitboard side. The connector is advantageously fitted directly onto thecover.

[0015] In a preferred embodiment, the device has bearing with twobearing bushes, one attached to the rotating element and the otherattached to the non-rotating element, with rollers being mounted betweenthe two bushes.

[0016] The rotation parameter detection means advantageously includes asensor attached to the fixed element and an encoder attached to therotating element. As a variant, to improve the redundancy of themeasurement, two sensors may be provided and mounted onto the fixedelement at two peripheral positions. The sensors and encoder may also bemounted directly onto the roller bearing bushes. In all cases, eachsensor has a connection output directly linked to the electronic signalprocessing means. This avoids the use of any connector cables.

[0017] In a preferred embodiment, the fixed element has a tubularportion and a radial portion equipped with means for attaching thedevice to a support. The rotating element has a tubular portion and aradial portion equipped with means for attaching a drive element, suchas a control wheel.

[0018] The invention will be better understood after studying aparticular embodiment described by way of example and in no wayrestrictive, illustrated in the appended figure, which shows an axialcross-sectional view of an embodiment of an instrumented roller bearingaccording to the invention.

[0019] In the illustrated embodiment, the instrumented roller bearinghas an external element 1 designed to house and attach the rollerbearing, of annular shape, featuring a tubular section 2 and a radialportion 3 stretching from one end of the tubular section towards theoutside. The radial portion 3 is provided with a number of attachmentholes 4 suitable to accept screws to attach it to a fixed cage 5, shownschematically.

[0020] The roller bearing has amongst others an internal element 6centred on the same axis 7 as the external element 1. The internalelement 6 has a U section annular shape and has a tubular portion 8, oneend of which is enclosed by a radial portion 9. There are a number ofholes 10 provided through the tubular portion 9 to accommodate screwsshown in 11, for example designed to attach a rotary movement wheel 12,shown schematically in dotted lines.

[0021] The external 1 and internal 6 elements are made of xxx s in theexample shown.

[0022] In the embodiment illustrated a roller bearing 13 is shownbetween the external 1 and internal 6 elements. The roller bearing 13has a row of balls 14 disposed between an external bush 16 mountedinside the bore of the tubular portion 2 of the external element 1, andan internal bush 16 mounted on the tubular portion 8 of the internalelement 6.

[0023] In one variant, it could be provided that rolling elements suchas balls 14, needles, etc. be mounted directly in contact with theexternal 1 and internal 6 elements by means of bearing races provided onthe said external and internal elements.

[0024] The external bush 15, fitted into the bore of the tubular portion2 of the external element 1, is provided with a bearing race 15 a forthe rolling elements 14. The internal bush 16, fitted onto the outsidejournal of the tubular portion 8 of the internal element 6, is providedwith a bearing race 16 a for the rolling elements 14. The external bush15 is among others equipped with two symmetrical grooves 18 and 19 onits bore, on either side of the bearing race 15 a. The groove 18 permitsa seal 20 to be fitted that is in contact with one of the thrust facesof the internal bush 16. The groove 19 permits a sensor unit to beattached, this assembly is referenced 21.

[0025] In the illustrated example, the sensor unit 21 has two detectorelements 22, 23, made for example in the form of Hall effect cells,positioned diametrically opposite one another and moulded into asynthetic material forming an annular part 24 of the sensor unit 21. Thesensor unit 21 is attached to the front face of the external bush 15 bymeans of an annular axial portion 25, which co-operates with the groove19 and is partially housed inside the bore of the non-rotating externalbush 15, so that the detection elements 22, 23 may be partially disposedbetween the two bushes 15 and 16.

[0026] As a variant, the sensor unit may also be fixed not ton theexternal bearing bush but on the tubular portion 2 of the externalelement 1, for example by a tight press fit into the bore of the tubularportion 2.

[0027] The two detection elements 22, 23, each co-operate with a singleencoder ring 31, mounted opposite the sensor unit 21 on the externalcylindrical surface of the inside rotating bush 16, so that it is drivenin rotation by the latter. The encoder ring 31 may be made for examplein the form of a multi-polar magnetic ring. The encoder ring 31 ismounted on a support 32 which is partially housed between the bushes 15and 16. The support 32 is of T section and annular shape, and isattached onto the external cylindrical surface of the rotating bush 26and is in contact with a face of it. One portion of the encoder ring 31is thus situated between the bushes 15 and 16 and another portionprojects outwards. The majority of the external cylindrical surface ofthe encoder ring 31 is opposite the two detector elements 22, 23 with asmall air gap.

[0028] A brake, not shown in the diagram, may also be provided in orderto generate a friction torque between the rotating parts and the fixedparts, and therefore improve the precision of the rotational movementsof the control wheel. By way of example of such a brake, we can mentionthe French patent application n° 2 782 970.

[0029] The detection of the rotation parameters of the internal rotatingbush 16 and consequently of the control wheel is carried out by theencoder ring 31, which moves in front of the sensor unit 21 equippedwith its two independent sensors 22, 23. Each of the sensor elements 22,23 supplies its own information redundantly on the angular displacementof the encoder 31 to the electronic information processing circuit. Eachsensor 22, 23, may advantageously include two independent sensors, inorder to provide information both on the value and the direction of theangular displacement.

[0030] A printed circuit board 33, positioned in a radial plane in theaxial continuation of the bearing, is fixed to the sensor unit 21 by anyappropriate means such as screws, clips, gluing, ultrasonic welding,etc. The printed circuit board 33 has both electronic signal processingmeans 34 and electronic means 35 that form a steering logic for anactuator referenced 36, and illustrated on the figure in dotted lines.The actuator 36 may be, for example, an electrical or electro-hydraulicjack used to turn the wheels of a vehicle. The sensors 22, 23 aredirectly connected to the printed circuit of the board 33 by the shortconnections 22 a, 23 a. The connection between the detection means, theelectronic signal processing means and the steering logic electronicmeans is therefore direct, in a very compact space and without the useof external connector cables. This therefore avoids the disadvantagespreviously mentioned related to the use of such cables.

[0031] The device assembly is enclosed on its printed circuit board 33side by a cover 37, made for example of a synthetic material and fixedby any appropriate means to the outside edge of the tubular portion 2 ofthe external element 1.

[0032] In the embodiment illustrated, the cover 37 has among others aconnector 38 whose pins 39 are electrically connected directly to theoutput of the steering electronic means on the printed circuit board 33.Once again, the connection is practically direct, without connectorcables, very compact and avoiding any risk of damage.

[0033] The transmission to the actuator 36 of the steering ordersresulting from the rotation of the control wheel 12 is made by the cable410 that is directly connected to the connector 38.

[0034] In one variant of the invention, the outside element 1 mayinclude a radial base wall extending towards the inside from the freeedge of the tubular portion 2 opposite the radial portion 3, axiallyenclosing the housing defined radially by the tubular portion 2. Thdetection means ad the printed circuit board would then be housed in aspace enclosed axially by the said radial wall, and on the opposite sideby the roller bearing 13, without any need for an additional cover 37.Of course, connections for the cable 40 and the printed circuit board 33would be provided.

[0035] The device of this invention has a number of advantages. First ofall, its great simplicity allows it to be manufactured cheaply.Furthermore, its modularity allows it to be adapted with a same basicroller bearing structure to different applications by simply changingthe printed circuit board. It is extremely reliable when handling thebearing, as all of the elements and parts are totally protected.Finally, the device is very easy to install, it is a single unit thatcomprises the support and attachment means of the control wheel and allelectronic means. Once the device is fitted to the vehicle or machine,then the control wheel just has to be fitted onto the internal rotatingelement 6 and the cable 40 connected to the output connector 38 to makethe device work.

[0036] The sensor unit 21 and the encoder ring 31 are in direct contactwith the bushes 15, 16, which makes the instrumented roller bearing morecompact axially.

[0037] The printed circuit board 33 is positioned so that it is incontact with the sensor unit 21 and housed with the detection assemblyin the tubular portion 2 that also houses the roller bearing 13. Thismakes possible an assembly that is radially compact, comprisingdetection means and actuator steering means.

[0038] Of course, within the context of this invention, it is possibleto provide for the installation of the detector unit directly onto theroller bearing bushes instead of on a separate element, as shown in theexample illustrated. Even though, in the example illustrated, tworedundant sensors have been used, it is understood that a detectorsystem can be envisaged with a single sensor. Finally, withoutfundamentally changing the organisation of this invention, it can beenvisaged that the external element rotates, while the internal elementis fixed.

1. Instrumented roller bearing, in particular for a control wheel (12)comprising an external element (1) and an internal element (6), one ofwhich rotates while the other is fixed, by means of at least one row ofrollers (14) disposed between the said elements, and a means ofdetection (22, 23, 31) of the rotation parameters of the rotatingelement, characterised in that it comprises among others electronicmeans (34) for processing the signals emitted by the detection means andelectronic steering means (35) for at least one actuator (36)electrically linked to the device.
 2. Device of claim 1, characterisedin that the electronic means for processing the signals and theelectronic steering means are mounted on a printed circuit board (33)fixed in rotation.
 3. Device of any of claims 1 or 2, characterised inthat a connector (38) is directly linked to the electronic steeringmeans and can co-operate with a connector cable (40) linked to theactuator (36).
 4. Device of any of the previous claims, characterised inthat it includes a cover (37) that encloses the device on the side wherethe printed circuit board (33) is situated.
 5. Device of claim 4,characterised in that the cover (37) comprises a connector (38) that isdirectly linked to the electronic steering means and can cooperate witha connector cable (40) linked to the actuator (36).
 6. Device of any ofthe previous claims, characterised in that it comprises two bearingbushes (15, 16), one of which is attached to the rotating element andthe other is attached to the non-rotating element, and between them aredisposed rolling elements.
 7. Device of claim 6, characterised in thatthe detection means of the rotation parameters comprise at least onesensor (22, 23) attached to the non-rotating bush co-operating with anencoder (31) attached to the rotating bush.
 8. Device of claim 6,characterised in that the detection means of the rotation parameterscomprise at least one sensor (22, 23) attached to the non-rotatingelement co-operating with an encoder (31) attached to the rotatingelement.
 9. Device of any of claims 7 or 8, characterised in that eachsensor (22, 23) comprises a connection output (22 a, 23 a) directlylinked to the electronic signal processing means.
 10. Device of any ofthe previous claims, characterised in that the fixed element comprises atubular portion (2) and a radial portion (3) equipped with means (4) forattaching the device to a support.
 11. Device of any of the previousclaims, characterised in that the rotating element (6) comprises atubular portion (8) and a radial portion (9) equipped with means (10)for attaching a drive part such as a control wheel (12).